He was a high elected official of the Oil, Chemical and Atomic Workers International Union (OCAW), serving as vice president from 1977 to 1988, and as secretary-treasurer from 1988 to 1991.
His mother died of cancer when Mazzocchi was six years old, and the family lost their home because of the cost of her medical care.
These early influences and experiences played a major role in forming Mazzocchi's radically progressive political views.
[3] Lying about his age, he enlisted in the United States Army, and fought in Europe during World War II as an anti-aircraft gunner.
[1][6] In 1953, at the age of 26, Mazzocchi was elected president of the United Gas, Coke, and Chemical Workers' Union (UGCCWU) Local 149, having run on a pledge of equal pay for women.
[1][4] In the 1960s, Mazzocchi was one of the first labor leaders to begin building strong ties with the environmental movement, an effort which paid off in the passage of major federal worker legislation.
[4][6] He used his position to push strongly for health and safety language in union contracts, as well as for state and federal legislation on the issue.
[4] In 1969 and 1970, he organized a series of public meetings in which OCAW and other union members testified about the chemicals they were handling and the health problems they were having.
The media attention and pressure from union members provided critical support for congressional attempts to pass comprehensive occupational health and safety legislation.
In December 1970, Congress enacted and President Richard Nixon signed the Occupational Safety and Health Act (OSHA).
Nixon specifically cited Mazzocchi's leadership and grassroots organizing efforts as key in winning passage of the Act.
[1][4][6][12] Because of his strong ties to the environmental movement, Mazzocchi was named chair of the first Earth Day rally in New York City on April 22, 1970.
[14] After becoming legislative director for OCAW, Mazzocchi began a worker education campaign on the dangers of asbestos in the workplace.
Workers with asbestosis, lung cancer, and peritoneal mesothelioma played a prominent role in the occupational health and safety conferences he organized as part of his OSHA campaign.
[15] But Mazzocchi believed the OSHA standard was too lenient, and worked to have the National Institute for Occupational Safety and Health conduct additional research into the toxicity of asbestos.
When speaking during the 1960s about the exposure of hundreds of workers to asbestos in Tyler, Texas, he said: I wanted the whole country to know in detail what had happened at that factory, and to understand what had gone on there—the fruitless...lack of enforcement by the Department of Labor, the whole long lousy history of neglect, deceit and stupidity—was happening in dozens of other ways, in hundreds of other factories, to thousands of other men across the land.
Silkwood, a newly elected union representative, came to suspect that Kerr-McGee officials were falsifying records about the integrity of the plant's plutonium nuclear fuel rods.
[17][18] Mazzocchi arranged for the three to testify before the Atomic Energy Commission (AEC) regarding safety failures at the Crescent plant.
Mazzocchi believed that by leaking information to the press and following up with public testimony, he could create the same outcry for change that had proven so successful in the OSHA campaign.
[4][17][18] When Silkwood discovered in early November that she had been contaminated with dangerous levels of plutonium, Mazzocchi feared that Kerr-McGee might pinpoint her as the source of the information OCAW intended to leak to The New York Times.
[4][17] Karen Silkwood died in a car accident on November 13, 1974 while on her way to deliver evidence to New York Times reporter David Burnham about the safety violations at the Crescent plant.
[4][17] The NLRB issued a complaint against Kerr-McGee for violating the National Labor Relations Act, but never sought court enforcement of its order.
[4][17] Although Mazzocchi continued to fight for worker health and safety issues at Kerr-McGee,[23] he was compelled in 1975 to cease any further investigations into Silkwood's death.
But the disaffiliation of most of OCAW's Canadian membership[24] and the breakup of the environmental-union coalition over the issue of job protections[25] led to a second defeat (again by less than 1 percent of the vote).
[26] Estranged from the OCAW leadership,[7] Mazzocchi spent much of the early 1980s agitating for more aggressive organizing and stronger stands on occupational health and safety.
[28] He drew national attention to industry efforts to force women who worked with toxic chemical to undergo sterilization.
[4][8] His activities in SANE won him a meeting in 1964 with President Lyndon B. Johnson to discuss converting military production facilities to civilian use.